Pneumatic relay



June 14, 1927'.

E. w. GENT PNEUMATIC RELAY Filed 09612, 1925 Wren/0r:

manner so that the free end of the bellows is balanced then the spring 31 is employed for adjustment by turning the screw '19.

, may be traced from the positive terminal of the battery 17 conductor 18, screw 19,

post 20, arm 27, contact 28 of the terminal 88,-conductor 29, lamp 30 and thence to the negative terminal of the battery 17 over the conductor 26. When the air is exhausted from the chamber &0, due to a blockade in the tube 16, the bellows fills out, or in reality, expands, therefore closing the arm 22 against the contact 23. The closing of this contact establishes a circuit which may be traced as follows: From the positive terminal of the battery 17, conductor 18, screw 19,,post 20, arm 22, contact 23 of'the terminal 37, conductor 24, lamp 25, conductor 26, and thence to the negative terminal of the battery. Lamp 25 lights in this circuit to indicate the blockade and its location as above described. It is of note that the bellows ismade of very thin woven material such as the bellows cloth used in player pianos. Furthermore, as illustrated on the drawing, due to the material used and its structure, the bellows is readily collapsible and not merely extensible as isthe usual accordion type bellows. In other words, upon a decrease of pressure within the bellows the sides'thereof tend to collapse in the center so that a plane therethrough would be of comparatively smaller diameterthan the diameter of an end portion. Normally, for a bellows four inches'in diameter and four inches long, it hasbeen found that a collapsed condition reducing the diameter about 1/ at the center, gives satisfactory results. Furthermore, it is found that a 'difierence 1n the pressures within and with- .out the bellows whose equivalent may be measured by a force as low as that represented by lfl alcohol is sufficient to cause this collapsible condition to occurand operate the lever, controlling the indicating lamps. This is readily explained when it .is realized what acomparatively tremendous force a collapsing condition has due to a decrease in PTGSSHI'G'WltlllD the bellows.

'This collapsing action, it has been found exerts a force upon the end of the bellows controlling the lever,'far greater-than that possible with the accordion extensible tyl e bellows where the force is merely the equivalentofthe product of the difference in the pressures within and without the bellows When the reverse action takes place and the pressure in the bellows is greater than 'the'pressure without it, the force exerted by the bellows-per se, will be equal to theprodnot of the difference in pressure times the area of the end section. However, in order that the device he operable for small varia tions in'pressure, the freeend ofthe bellows to which the lever is attached is made of comparatively heavy material such as'phenol fibre about thick. Consequently, this weight downward, in combination with the force duejto the difference inpressure, is

sufficient to give a result upon the clog ing of one tube as satisfactory as'that obtained by the aforementioned collapsing condition, when the other tube is effected.

lVhat is claimed is:

1. A pneumatic relay comprising a sealed chamber, a bellows within said chamber mounted in an upright position and constructed to assume a collapsible position when its inner pressure is lessthan'that of said chamber, a support within the chamber for rigidly supporting the bellows at its top, a base *for the free end of said bellows made of comparatively heavy material, a lever pivoted at or nearits mid-point with one end secured to the bottom of said 'bellows so that when the pressure within said "bellows is less than the pressure within said 'than'the pressure within said chamber, said lever is moved-in the other direction by the expansion of the bellows and the weight of the base of the bellows, and electrical contacts operated by the .movement of said lever to control signals to indicate the po-- sition of greatest pressure.

2. A pneumatic relay comprising a sealed chamber, a bellows within said chamber mounted in an upright position and constructed to assume a collapsible position when its inner pressure is less than that of said chamber, a support within the chamber for rigidly supporting the bellows at its top, a base for the free end of said bellows made of comparatively heavy material, a lever pivoted at or near its mid-point with one end secured to the bottom of said bellows so that when the pressure within said bellows is less than the pressure within said chamber said lever ismoved in one direction by the collapse of the bellows and, when the pressure within said bellows is greaterthanthe pressure within said chamber, said lever is moved in the other direction by the expansion of the bellows and the weight of the base of the bellows, electrical contacts operated by the lever to control signals to indicate the position of greatest pressure, and an adjustable tensioning device Within said chamber cooperating with said lever and adapted to be controlled without said chainher for normally maintaining all of said electrical contacts open. ,7 In wltness whereof, I hereunto subscribe 10 my name this 5th day of December A; D.,

EDGAR GENT. 

